1. Field of the Invention
This invention relates to a centrifugal separator with a function for detecting information regarding the used rotor.
2. Description of the Prior Art
In a centrifugal separator having an attachment for attaching one of different (types of) replaceable rotors thereto, it is desirable to detect the type of the attached rotor. Japanese utility model No. 1941678 discloses a technique of detecting position angles of identification marks arranged on a circular circumference of the rotor to determine the used rotor. Another prior art centrifugal apparatus is described in Japanese patent application No. 2000-307012 (filed on Oct. 6, 2000) which was applied by the same assignee of this application (corresponding U.S. patent application Ser. No. 09/969,807), wherein the time intervals of the detected identification marks are measured while the rotational speed of the rotor is constant. The type of the attached rotor is judged from angular intervals of the identification marks obtained from the product of the measured time intervals and the rotational speed.
Because this measurement is done at a constant speed during the starting period of rotation, the acceleration interval becomes longer.
If this measurement would be done while the rotation of the rotor is being accelerated, the measurement error will occur. Therefore, it is required to accurately detect the angular intervals of the identification marks on the rotor during acceleration of the rotation of the rotor.
The aim of the present invention is to provide a superior centrifugal separator.
According to the present invention, a first aspect of the present invention provides a centrifugal separator comprising:
a rotating unit having a rotation axis;
a rotor attaching means for attaching one of different replaceable rotors to said rotation axis, each of said rotors having a plurality of identification marks arranged on a circumference defined by said rotation axis on a surface thereof with angular intervals which are predetermined for each of said different rotors;
identification mark detection means for detecting said identification marks in accordance with rotation of said attached rotor;
a rotation detector for detecting rotation of said rotation axis to generate a rotational speed signal; and
detection means responsive to said identification mark detection means and said rotational speed signal for detecting said angular intervals to identify said attached rotor, wherein said detection means measures rotating speeds from said rotational speed signal at first detection of one of said identification marks and second detection of said one of identification marks after one rotation of said rotation axis from said first detection, measures time intervals of said detected identification marks from said first detection to said second detection, calculates calculation rotational speeds of said rotation axis when others of said identification marks are detected from said measured time intervals and from said rotational speeds at said first and second detections, and integrates said measured rotational speeds and said calculation rotational speeds with said measured time intervals to calculate said angular intervals, respectively, to identify said one of rotors attached to said rotating unit.
According to the present invention, a second aspect of the present invention provides the centrifugal separator based on the first aspect, wherein said rotation detector generates said rotational speed signal with a predetermined number of pulses being generated per said rotation with a first resolution which is lower than a second resolution in the calculated angular interval.
According to the present invention, a third aspect of the present invention provides the centrifugal separator based on the first aspect further comprising compensation means for compensating said rotational speeds at said first and second detections with a total of said measured time intervals from said first detection to said second detection.